KiCad - A Cross Platform and Open Source Electronics Design Automation Suite
Unity - The multiplatform game creation tools for everyone.
Fritzing - Fritzing is an open-source initiative to support designers, artists, researchers and hobbyists to...
Godot Engine - Feature-packed 2D and 3D open source game engine.
LTspice - LTspice® is a high performance SPICE simulation software, schematic capture and waveform viewer with enhancements and models for easing the simulation of analog circuits.
Blender - Blender is the open source, cross platform suite of tools for 3D creation.